Central Nervous System: Spinal Cord and Brain Lecture Flashcards

100 vocabulary-style flashcards covering the central nervous system, spinal cord anatomy, reflexes, and major brain regions based on lecture notes.

Central nervous system

Refers to the nerves and brain.

Cervical enlargement

A thickened region of the spinal cord that innervates the shoulder and upper limbs.

Lumbar enlargement

A thickened region of the spinal cord that innervates the pelvis and lower limbs.

Conus medullaris

The tapered, inferior tip of the spinal cord found at or below the $L_1$ or $L_2$ vertebral level.

Cauda equina

A bundle of spinal nerve roots extending from the conus medullaris that resembles a horse's tail.

Filum terminale

A slender strand of fibrous tissue that extends from the conus medullaris to provide longitudinal support to the spinal cord.

Posterior median sulcus

A shallow longitudinal groove on the posterior surface of the spinal cord.

Anterior median fissure

A deep groove along the anterior surface of the spinal cord.

White matter

Regions of the nervous system consisting primarily of myelinated and unmyelinated axons.

Gray matter

Regions of the nervous system containing the cell bodies of neurons, neuroglia, and unmyelinated axons.

Central canal

A narrow internal passageway within the spinal cord filled with cerebrospinal fluid.

Dorsal root

The part of a spinal nerve that contains the axons of sensory neurons.

Ventral root

The part of a spinal nerve that contains the axons of motor neurons.

Dorsal root ganglion

A collection of sensory neuron cell bodies located near the spinal cord.

Spinal nerve

Formed by the union of the dorsal and ventral roots; contains both sensory and motor fibers.

Pia mater

The innermost layer of the meninges, consisting of a meshwork of elastic and collagen fibers firmly bound to the neural surface.

Arachnoid mater

The middle meningeal layer that includes a simple squamous epithelium and a network of collagen and elastic fibers.

Dura mater

The tough, fibrous outermost layer of the meninges.

Subarachnoid space

The interval between the arachnoid membrane and the pia mater, containing cerebrospinal fluid and blood vessels.

Epidural space

A region between the dura mater and the walls of the vertebral canal containing adipose tissue and blood vessels.

Denticulate ligaments

Extensions of the pia mater that connect to the dura mater to prevent lateral movement of the spinal cord.

Nuclei

Functional groups of neuron cell bodies situated in the CNS.

Sensory nuclei

Nuclei in the spinal cord that receive and relay sensory information from peripheral receptors.

Motor nuclei

Nuclei in the spinal cord that issue motor commands to peripheral effectors.

Posterior gray horn

Region of spinal gray matter containing somatic and visceral sensory nuclei.

Anterior gray horn

Region of spinal gray matter containing somatic motor nuclei.

Lateral gray horn

Region of spinal gray matter found only in the thoracic and lumbar segments, containing visceral motor nuclei.

Gray commissures

Narrow bridges of gray matter posterior and anterior to the central canal.

Tract

A bundle of axons in the CNS that are uniform in diameter and myelination, carrying the same type of information in the same direction.

Ascending tracts

Axon bundles that carry sensory information toward the brain.

Descending tracts

Axon bundles that convey motor commands to the spinal cord.

Epineurium

The outermost connective tissue layer of a spinal nerve, consisting of a dense network of collagen fibers.

Perineurium

Connective tissue layer that divides a nerve into a series of compartments containing bundles of axons called fascicles.

Endoneurium

The innermost connective tissue layer of a nerve that surrounds individual axons.

Nerve

A bundle of axons located in the Peripheral Nervous System (PNS).

Ganglion

A collection of neuron cell bodies located in the Peripheral Nervous System (PNS).

Dorsal ramus

A branch of a spinal nerve that provides sensory and motor innervation to the skin and muscles of the back.

Ventral ramus

A branch of a spinal nerve that provides sensory and motor innervation to the body wall and limbs.

Rami communicantes

Nerve branches containing autonomic fibers that lead to a sympathetic ganglion.

Dermatomes

Specific regions of the skin surface monitored by a single pair of spinal nerves.

Shingles

A condition caused by a virus that infects a specific spinal nerve, often diagnosable via a dermatome pattern.

Interoceptors

Sensory neurons that monitor internal systems and provide sensations of distension, deep pressure, and pain.

Proprioceptors

Sensory neurons that monitor the position and movement of skeletal muscles and joints.

Exteroceptors

Sensory neurons that provide info about the external environment, such as touch, pressure, and special senses.

Sensory neurons (quantity)

Approximately $10 \text{ million}$ in the human body.

Motor neurons (quantity)

Approximately $0.5 \text{ million}$ in the human body.

Interneurons (quantity)

Approximately $20 \text{ billion}$ in the human body.

Decussation

The crossing of nerve fibers from one side of the spinal cord or brain to the other.

Plexuses

A complex, interwoven network of nerves, such as the cervical, brachial, lumbar, and sacral plexuses.

Neuronal pools

Functional groups of interconnected neurons in the Central Nervous System (CNS).

Divergence

The spread of information from one neuron to several neurons or pools, allowing broad distribution.

Parallel Processing

When several neurons or pools process the same information simultaneously.

Serial Processing

Occurs when information is relayed in a stepwise fashion from one neuron or pool to the next.

Convergence

Several neurons synapsing on a single postsynaptic neuron, allowing different sources to cause the same response.

Reverberation

A positive feedback loop where collateral branches of axons loop back to stimulate presynaptic neurons.

Reflex arc

The specific nerve pathway of a single reflex, typically involving a receptor, sensory neuron, CNS processing, motor neuron, and effector.

Innate reflexes

Genetically or developmentally programmed reflexes that appear in a predictable sequence, such as sucking or tracking with eyes.

Acquired reflexes

Complex, learned motor patterns enhanced by repetition, also known as conditioned reflexes.

Somatic reflexes

Reflexes that provide for the involuntary control of skeletal muscles.

Visceral reflexes

Autonomic reflexes that control or adjust activities of smooth muscle, cardiac muscle, glands, and adipose tissue.

Monosynaptic reflex

The simplest reflex arc involving only one synapse in the CNS, where a sensory neuron synapses directly with a motor neuron.

Polysynaptic reflex

Reflexes involving at least one interneuron between the sensory and motor neuron, resulting in a longer delay.

Spinal reflexes

Reflexes where the important interconnections and processing occur in the spinal cord.

Cranial reflexes

Reflexes where the processing occurs in the brain, such as pupil dilation or eye tracking.

Stretch reflex

A monosynaptic reflex that automatically regulates skeletal muscle length, such as the patellar reflex.

Muscle spindles

Sensory receptors in the stretch reflex consisting of a bundle of small, specialized intrafusal muscle fibers.

Reciprocal inhibition

The process where interneurons stimulate one group of muscles (flexors) while inhibiting the opposing group (extensors).

Ipsilateral

A reflex where the sensory stimulus and the motor response occur on the same side of the body.

Contralateral

A reflex where the motor response occurs on the side opposite the stimulus, such as the crossed extensor reflex.

Babinski sign

The fanning of toes when the lateral sole of the foot is stroked, normal in infants but indicates CNS damage in adults.

Plantar reflex

Normal adult response to stroking the foot, characterized by a curling of the toes (flexion).

Neural tube

The embryonic structure formed from the neural groove that develops into the Central Nervous System.

Prosencephalon

Primary brain vesicle also known as the forebrain.

Mesencephalon

Primary brain vesicle also known as the midbrain.

Rhombencephalon

Primary brain vesicle also known as the hindbrain.

Telencephalon

Secondary brain vesicle that develops into the cerebrum.

Metencephalon

Secondary brain vesicle that develops into the pons and cerebellum.

Myelencephalon

Secondary brain vesicle that develops into the medulla oblongata.

Ventricles

Chambers within the brain filled with cerebrospinal fluid.

Septum pellucidum

A thin partition that separates the two lateral ventricles of the cerebral hemispheres.

Dural sinuses

Large collecting veins located within the dural folds.

Choroid plexus

A combination of specialized ependymal cells and capillaries that produces and maintains cerebrospinal fluid.

Arachnoid granulations

Fingerlike extensions of the arachnoid membrane used for the reabsorption of CSF into the venous circulation.

CSF daily production

Approximately $500\,mL$ is produced per day.

Gyri

Elevated ridges or folds on the surface of the cerebral cortex.

Sulci

Shallow depressions on the cerebral surface that separate the gyri.

Fissures

Deep grooves that subdivide the cerebral hemispheres, such as the longitudinal fissure.

Basal nuclei

Subcortical motor centers that provide subconscious control of skeletal muscle tone and coordination of learned patterns.

Precentral gyrus

The gyrus of the frontal lobe that contains the primary motor cortex.

Postcentral gyrus

The gyrus of the parietal lobe that contains the primary somatic sensory cortex.

Word salad

A symptom of damage to the speech center in the left hemisphere where a person can speak but their words are disorganized and nonsensical.

Corpus callosum

A massive bundle of commissural fibers that connects the two cerebral hemispheres.

Thalamus

The final relay point for all ascending sensory information, involved in memory and emotional processing.

Hypothalamus

The chief integration center for the autonomic nervous system that regulates body temperature, food intake, and thirst.

Limbic system

A functional system that establishes emotional states and facilitates memory storage and retrieval.

Amygdaloid body

A limbic structure that regulates heart rate and the fight or flight response and links emotions to memories.

Hippocampus

A structure in the limbic system essential for learning and the storage/retrieval of long-term memories.

Orexins

Wake-up chemicals secreted by hypothalamic nuclei; their selective destruction is associated with narcolepsy.

Reticular activating system (RAS)

A component of the reticular formation responsible for maintaining consciousness and alertness.

Cerebellum

The brain region responsible for balance, posture, and smooth, coordinated skeletal muscle movements.